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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
1/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
Organization (S):
EDF-R & D/AMA















Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
Document: V6.04.165



SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY




Summary:


This test makes it possible to validate the mechanical law elastoplastic Cam_Clay specific to the grounds normally
consolidated. This law integrates an elastoplastic hydrostatic mechanism (of which the elastic part is
non-linear and the threshold of flow corresponds to the pressure of consolidation) coupled to a mechanism
deviatoric elastoplastic the elastic part is linear. The behavior is hardening or
softening according to the combination of the two mechanisms.
This test carried out in hydro-mechanical coupling includes/understands two ways of loading:
1) a hydrostatic way of compression in condition drained until the pressure of consolidation,
2) a way not-drained by maintaining the pressures lateral confining on the sample and by imposing one
vertical displacement of compression which induces a triaxial state of stresses.
Modeling is carried out in 3D.
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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
2/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
1
Problem of reference
1.1 Geometry
Z
X
y
L
H
E
height: H = 1m
width: L = 1 m
thickness: E = 1 m
1.2
Properties of material
6
4
.
22 E
E
=
AP
3
.
0
=
5
.
1
-
=
E
Parameters specific to CAM_CLAY:
14
.
0
=
PORO
,
25
.
0
=
,
05
.
0
=
,
9
.
0
=
M
,
5
.
3
_
E
CRIT
NEAR
=
AP,
5
.
1 E
AP
=
AP
1.3
Boundary conditions and loadings
The first way of loading is carried out with a state of hydrostatic stresses:
P
zz
yy
xx
=
=
=
. One makes a first elastic design until
AP
P
=
(to establish an initial state).
One increases then
P
until
Cr
ion
consolidat
P
AP
E
P
P
2
5
.
6
sup
=
=
=
by using Cam_Clay,
pressure of water is null
0
1
=
PRE
(drained condition). For the second way, one maintains
pressure
P
on the side faces and one imposes then a vertical displacement imposed in
compression to modelize a triaxial compression test, calculation is now not drained, which corresponds to
a hydrostatic flow no one on all the faces.
1.4 Conditions
initial
In
CAM_CLAY
, the elastic law requires a hydrostatic stress strictly higher than zero with
the initial state (deformation being null).
To initialize this stress, one chose to carry out at the beginning a purely elastic calculation in
making evolve/move pressure of 0. with 1.E5 AP. One extracts from this calculation only the field of
stresses at the points of gauss. This stress field resulting from the elastic design is considered
like the initial state of the hydrostatic stress necessary to the law Cam_Clay of following calculation.
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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
3/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
2
Reference solution
An exact solution exists as much as the loading is hydrostatic (cf SSNV160). For the second
triaxial way, an analytical solution is not obvious to find. In the same way, one does not have
data and of triaxial experimental test results allowing to compare with calculations.
This test is a test of not-regression.
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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
4/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
3 Modeling
With
3.1
Characteristics of modeling
Modeling 3D
Z
X
y
NO12
NO2
NO3
NO10
NO9
NO13
NO15
NO14
NO11
NO20
NO19
NO18
NO1
NO7
NO6
NO8
NO16
NO4
NO5
NO17
3.2
Characteristics of the mesh
A number of nodes:
20
A number of meshs:
1 of type HEXA 20
6 of type QUAD 8

The following meshs are defined:
STRAIGHT LINE
NO3 NO5 NO8 NO10 NO12 NO15 NO17 NO20
LEFT
NO1 NO4 NO6 NO9 NO11 NO13 NO16 NO18
IN FRONT OF
NO6 NO7 NO8 NO11 NO12 NO18 NO19 NO20
BEHIND
NO1 NO2 NO3 NO9 NO10 NO13 NO14 NO15
LOW
NO13 NO14 NO15 NO16 NO17 NO18 NO19 NO20
HIGH
NO1 NO2 NO3 NO4 NO5 NO6 NO7 NO8
To account for the 1/8
ème
structure, the boundary conditions in displacement imposed are:
On the LOW face: DZ = 0
On the LEFT face: DY = 0
On the face BEHIND: DX = 0
The loading is consisted of the same pressure divided into compression on the 3 meshs: `HIGH,
“RIGHT” and “IN FRONT” to simulate a hydrostatic test with
0
1
=
PRE
in drained. Then,
pressure distributed is maintained constant on the side faces “STRAIGHT LINE” and “IN FRONT”, one
displacement DZ is imposed on the variable face “HIGH” with time in not drained.
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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
5/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
3.3 Functionalities
tested
Controls
DEFI_MATERIAU CAM_CLAY
STAT_NON_LINE COMP_INCR




NEWTON
RELATION= `KIT_HM'
`RELATION_KIT'=
“CAM_CLAY”
“LIQU_SATU”
“HYDR_UTIL”
STAMP = TANGENT

3.4
Sizes tested and results
Components
xx
,
yy
and
zz
stress are tested at moments 3., 6., 15. and 20. and
value of the pressure of water PRE1 at moment 20 with nodes NO8. The values of reference are
values of not-regression.
Values of
xx
and
yy
:
Moment
Reference
Aster
1
Er
loading 3.
­ 3.000000+05 ­ 3.000000+05
1
Er
loading 6.
­ 6.000000+05 ­ 6.000000+05
2nd loading 15.
­ 2.590356+05 ­ 2.590355371917+05
2nd loading 20.
­ 2.495777+05 ­ 2.495776491115+05
Values of
zz
:
Moment
Reference
Aster
1
Er
loading 3.
­ 3.000000+05 ­ 3.000000+05
1
Er
loading 6.
­ 6.000000+05 ­ 6.000000+05
2nd loading 15.
­ 5.560431+05 ­ 5.650429335188+05
2nd loading 20.
­ 5.578873+05 ­ 5.578813428168+05
Values of PRE1:
Moment
Reference
Aster
2emechargement 20.
3.50422+05 3.50422350888+05
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Code_Aster
®
Version
6.4
Titrate:
SSNV165 - Triaxial compression test not drained with the law
CAM_CLAY
Date:
03/06/03
Author (S):
G. DEBRUYNE, J. EL GHARIB
Key
:
V6.04.165-A
Page:
6/6
Manual of Validation
V6.04 booklet: Nonlinear statics of the voluminal structures
HT-66/03/008/A
4
Summary of the results
By interpreting the diagram, (P, Q),
()
3
tr
P
-
=
and
)
(
1
3
-
-
=
Q
in the case of this case test, one
note well that the loading remains hydrostatic up to a value of
5
.
6th
AP. Once it
vertical displacement is imposed and varies with time, the pressures on the side faces being
maintained constant, a diverter of stresses is induced and increases with time with one
positive work hardening. When one approaches the point
MP
Q
=
, one tends towards perfect plasticity with
plastic flow without work hardening and variation of stresses (see [§6] Doc.
[R7.01.14]).